The present invention relates to a tying method and member for use in tying up the neck portion of a plastic bag (including a net bag) for containing processed foodstuffs, farm products or the like.
U.S. Pat. No. 3,021,354, for example, discloses a tying member for tying up neck portion of a plastic bag such as a bag of polyvinyl chloride. The tying member is provided with a slit for use in inserting the fastened neck portion of the bag into an opening for accommodating the neck portion, and thorns or projections extending from the peripheral edge of the opening to the center thereof.
Due to the fact that the outer end of the slit located on the outer peripheral edge of the tying member disclosed by the reference above is left open after the neck portion of the bag is tied up and closed, the neck portion of the bag may be forced out or otherwise the tying member itself may drop out of the neck portion thereof. Moreover, the shortcoming of the tying member is that the tying member may shift in the vertical direction of the bag thus tied up and consequently drop off the bag because the neck portion of the bag is only inserted through the slit into the opening of tying member.
On the other hand, Japanese Patent Laid-Open No. 4060/1987 discloses a tying member which is provided with an annular carrier, a plurality of elastic fingers projecting from the inner peripheral edge of the carrier toward the center thereof to form substantially a conical configuration, and an opening for receiving the neck portion of a bag in the center of the bag. This tying member features that the neck portion of the bag can readily be inserted. However, the tying member is still disadvantageous in that its tying force is weak even after the tying member is fitted to the neck portion of the bag through a slit between the elastic fingers and that, in view of its structure, the tying member tends to become costly.